ABSTRACT
The water separated out at the demulsication stage at oileld-processing facilities contains residual oil and nely dispersed solids. The oil is present as a dispersion in water or an oil-in-water emulsion (inverse emulsion). The concentration of residual oil is usually too high for discharge of the water to be allowed into the environment, plus the residual oil also has economic value.1 For example, a new discharge standard for oil and grease in produced water in the Northeast Atlantic and North Sea area of 30 ppm (30 mg/l, previously 40 mg/l) became effective on January 1, 2007. Elsewhere, this level may be set as low as 5-10 mg/l, which can be difcult to achieve. In addition, if the water is to be reinjected, the solids may plug the pore throats in the near-well area of the injection wells, or plug lters, raising back-pressures, which wastes energy, damages equipment, and can even lead to shutdown. Therefore, the water needs to be treated to remove the oil and dispersed solids. The chemical method of doing this is to add a occulant, also called a “water clarier,” “deoiler,” “oil-inwater demulsier,” “reverse emulsion breaker,” or “polyelectrolyte.” Flocculants can also be useful in wellbore cleanup operations.2
